ELTSHA MITCHEl.L SCIENTIFIC SOCIETY. 109 



whether very near a cvst or distant from it. The increase in 

 number of the wood and vascular cells of the central cylinder 

 takes place though the cyst may not be located in or very near 

 it. In such cases the fibres and ducts have their normal loniri- 

 tudinal direction. But if a cyst is located in or very near the 

 central cylinder the ducts are turned in their direction of growth 

 perpendicular to the axis of the root, bent around the cyst and 

 then converge on the peripheral side, when, left without any 

 controlling influence over their direction of growth, they often 

 perform very curious evolutions through the parenchymatous 

 tissue in all directions. 



A glance at Figs. 29 and 30, Plate V, will show at once a 

 great difference in the arrangement of the tissue elements and the 

 form of the cells of diseased roots compared with the same in a 

 healthy root. These figures represent sections of roots of the 

 cotton plant. Fig. 29 is fi-om a section through a gall on a 

 small lateral root, while Fig. 30 is from a healthy lateral root of 

 the same size as the non-infected portions of the root from which 

 Fig. 29 was taken. Both are drawn to the same scale and the 

 natural size of the lateral root from which Fig. 29 was made is 

 represented in Fig. 31. In the healthy lateral root (Fig. 30) it 

 will be noticed that the differentiation of the woody tissue, which 

 contains the large tracheal vessels, with the parenchyma is not 

 so marked as in most roots so that the stellate appearance is not 

 well represented. One of the most marked of the deformities 

 is the displacement of the liber fascicles. In Fig. 30 they are 

 shown in normal position at e. In Fig. 29 only one group is in 

 what would be the normal position if the root were not diseased 

 and of its normal size; this group is shown at e, Fig. 29; e^, e', 

 e\ e^, represent displaced groups; that is, in the rapid and abnor- 

 mal increase of wood cells from the central cylinder they have 

 been pushed far out of their normal position, while cells of the 

 parenchyma on the one side and wood cells on the other have 

 grown around the group e; e/ ' represents one group not displaced 

 but turned to grow in a tangential and radial direction, while 

 e' ' ' represents one group not only displaced, but turned also in a 

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